Data from: The Automated Root Exudate System (ARES): a method to apply solutes at regular intervals to soils in the field

1) Root exudation is a key component of nutrient and carbon dynamics in
terrestrial ecosystems. Exudation rates vary widely by plant species and
environmental conditions but our understanding of how root exudates affect
soil functioning is incomplete, in part because there are few viable
methods to manipulate root exudates in situ. To address this, we devised
the Automated Root Exudate System (ARES), which simulates increased root
exudation by applying small amounts of labile solutes at regular intervals
in the field. 2) The ARES is a gravity-fed drip irrigation system
comprising a reservoir bottle connected via a timer to a micro-hose
irrigation grid covering c. 1 m2; 24 drip-tips are inserted into the soil
to 4-cm depth to apply solutions into the rooting zone. We installed two
ARES subplots within existing litter removal and control plots in a
temperate deciduous woodland. We applied either an artificial root exudate
solution (RE) or a procedural control solution (CP) to each subplot for 1
min d-1 during two growing seasons. To investigate the influence of root
exudation on soil carbon dynamics, we measured soil respiration monthly
and soil microbial biomass at the end of each growing season. 3) The ARES
applied the solutions at a rate of c. 2 L m-2 wk-1 without significantly
increasing soil water content. The application of RE solution had a clear
effect on soil carbon dynamics but the response varied by litter
treatment. Across two growing seasons, soil respiration was 25% higher in
RE compared to CP subplots in the litter removal treatment, but not in the
control plots. By contrast, we observed a significant increase in
microbial biomass carbon (33%) and nitrogen (26%) in RE subplots in the
control litter treatment. 4) The ARES is an effective, low-cost method to
apply experimental solutions directly into the rooting zone in the field.
The installation of the systems entails minimal disturbance to the soil
and little maintenance is required. Although we used ARES to apply root
exudate solution, the method can be used to apply many other treatments
involving solute inputs at regular intervals in a wide range of
ecosystems.